Action Points

Diabetes and high BMI (≥25) were associated with an estimated 792,600 new cases of cancer, nearly 6% of all incident cancers, worldwide in 2012.

Note that most of the cancer cases attributable to diabetes and high BMI occurred in high-income western countries, followed by east and southeast Asian countries.

Diabetes and high BMI (≥25) were associated with an estimated 792,600 new cases of cancer, nearly 6% of all incident cancers, worldwide in 2012, British researchers reported.

In an analysis of 18 types of cancer in 175 countries, 544,300 cases were attributable to high BMI (equivalent to 3.9% of all cancers) and 280,100 were attributable to diabetes (2%), according to to Jonathan Pearson-Stuttard, BMBCh, at Imperial College London, and colleagues.

In the conservative estimate, diabetes and high BMI combined were related to approximately 4.5% (626,900 cases) of all incident cancers, they reported online in the Lancet Diabetes & Endocrinology.

Globally, the proportion of cancers linked to diabetes and BMI is expected to increase even further -- more than 30% in women and 20% in men on average -- as the prevalence of the two risk factors increases, the researchers added.

In an accompanying editorial, Yikyung Park, ScD, and Graham Colditz, MD, both of Washington University School of Medicine in St Louis, stated: "As predicted in this study, the global burden of cancer due to high BMI and diabetes will continue to increase unless the prevalences of these conditions fall. Both are preventable causes of cancer for which intervention is possible at multiple levels. More prompt actions are needed to help people maintain a healthy body weight throughout the life course, starting at an early age."

"The findings add another reason for the general public to be concerned about the health risks associated with obesity, which clearly include cancer," said Clifford Hudis, MD, CEO of the American Society of Clinical Oncology.

"Armed with this increasing recognition of its medical risks, we must work together across medical disciplines to help Americans address this challenge," noted Hudis, who was not involved in the study.

Pearson-Stuttard's group used comprehensive prevalence estimates of diabetes and BMI categories in 2002, assuming a 10-year lag between exposure to the conditions and incidence of cancer, along with relative risks from published estimates. They then used GLOBOCAN cancer incidence data to estimate the number of cancer cases attributable to the two risk factors. They reported 95% uncertainty intervals (95% UI) for estimates as the 2.5th to 97.5th percentile of the resultant distributions.

The authors found that most of the cancer cases attributable to diabetes and high BMI occurred in high-income western countries (38.2%, 303,000/792,600 cases), followed by east and southeast Asian countries (24.1%, 190,900 cases).

Incidence was less common in low and middle-income countries and varied by region. For example, between 9% and 14% of all cancer cases in Mongolia, Egypt, Kuwait, and Vanuatu were due to high BMI and diabetes, while less than 1% of all new cancer cases in Malawi and Tanzania were attributed to the conditions combined.

Cancer cases were almost twice as common among women (496,700 cases) compared with men (295,900 cases). In men, 126,700 cases (95% UI 95,900-159,400) were from liver cancer, constituting 42.8% of all cancer cases attributable to diabetes and high BMI combined in the independent estimate, followed by colorectal cancer (63,200 cases, 95% UI 40,600-86,000), making up 21.4% of the total cases.

Breast cancer was the leading type of cancer among women (147,400 cases, 95% UI 106,700-190,000), constituting 29.7% of all cancer cases, followed by endometrial cancer at 24.5% (121,700 cases, 95% UI 108,600-135,000).

The researchers also found that liver cancer and endometrial cancer led to the highest number of cancer cases caused by diabetes and high BMI (24.5%, 187,600/766,000 cases and 38.4%, 121,700/317,000 cases, respectively).

A study limitation was that the precision of the risk estimates used to adjust for common confounders, including diabetes and BMI, might have been affected by reverse causality and ascertainment bias. Additionally, the researchers noted that the 10-year lag between risk factor exposure and cancer development is only an estimate and may not include full exposure to the risk.

Colditz agreed, writing that "although the 10-year lag takes into account the process of carcinogenesis and cumulative exposure over time, it understates the importance of early life exposure, especially from high BMI, on cancer."

The study was funded by the NIHR and Wellcome Trust.

Pearson-Stuttard disclosed no relevant relationships with industry. A co-author disclosed relevant relationships with the Young Health Programme of AstraZeneca, Third Bridge, Scor, and Prudential.

Park and Colitz disclosed no relevant relationships with industry.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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